Memory Animal Research

Type of psychology: Biological bases of behavior; memory
Fields of study: Biological influences on learning; nervous system;
Pavlovian conditioning
Research with nonhuman animals has significantly contributed to an understanding
of the basic processes of memory, including its anatomy and physiology. Important
brain regions, neurotransmitters, and genes have been identified, and this information
is now being used to understand further and treat human memory disorders.

Key concepts
• anterograde amnesia
• engram
• experimental brain damage
• genetic engineering
• hippocampus
• prefrontal cortex
• retrograde amnesia
• stroke

Nonhuman animals have been used as subjects in memory research since
the earliest days of psychology, and much of what is known about the fundamental
processes of memory is largely based on work with animals. Rats,
mice, pigeons, rabbits, monkeys, sea slugs, flatworms, and fruit flies are
among the most commonly used species. The widespread use of animals in
memory research can be attributed to the ability systematically to manipulate
and control their environments under strict laboratory conditions and
to use procedures and invasive techniques, such as surgery and drugs, that
cannot ethically be used with humans. A typical research protocol involves
training animals on any of a variety of learning paradigms and concurrently
measuring or manipulating some aspect of the nervous system to examine
its relationship to memory.

Although learning and memory are closely related, a distinction should
be drawn between learning and memory. Learning is defined as a relatively
permanent change in behavior as a result of experience. Memory is the underlying
process by which information is encoded, stored, and retrieved by
the nervous system. Modern learning and memory paradigms are based on
the principles of classical and operant conditioning first established by the
early behaviorists: Ivan Pavlov, Edward L. Thorndike, John B. Watson, and
B. F. Skinner. These learning paradigms can be used to examine different
types of memory and to explore the underlying brain mechanisms that may
mediate them. For classical conditioning, widely used paradigms include
eyeblink conditioning, taste aversion learning, and fear conditioning. For
operant conditioning, memory for objects, spatial memory, context discrimination,
and maze learning are among the most frequently used procedures.
Two other very simple forms of learning, habituation (the gradual
decrease in response to a stimulus as a result of repeated exposure to it) and
sensitization (the gradual increase in response to a stimulus after repeated
exposure to it) are both simple forms of nonassociative learning also extensively
used in animal memory research.
Researchers have at their disposal a number of techniques that allow
them to manipulate the nervous system and assess its functions. Historically,
experimental brain damage has been one of the most widely used procedures.
This technique involves surgically destroying (known as lesioning)
various parts of the brain and assessing the effects of the lesion on memory
processes. Pharmacological manipulations are also frequently used and involve
administering a drug known to affect a specific neurotransmitter or
hormonal system thought to play a role in memory. Functional studies involve
measuring brain activity while an animal is actually engaged in learning.
Recordings can be made from individual brain cells (neurons), groups
of neurons, or entire anatomical regions. Beginning in the late 1990’s, genetic
engineering began to be applied to the study of animal memory.
These procedures involve the direct manipulation of genes that produce
proteins suspected to be important for memory.
By combining a wide variety of memory paradigms with an increasing
number of ways to manipulate or measure the nervous system, animal research
has been extremely useful in addressing several fundamental questions
about memory. These issues include the important brain structures involved
in memory, the manner in which information is stored in the
nervous system, and the causes and potential treatments for human memory
disorders. 525